The problem is not that my pc is too slow,i can even reach 700fps but i only want to raise the frame limiter to 60 instead 50. I'm playing ffx-2 on pcsx2 1.2.1. The game is an ISO and the video settings are:

Do you find that Ansiotropic Filtering at 16x slows down the game? I have a GeForce too.

Does turning Shade Boost, FX Shader and AA1 slow the game down?

The only time I use 8-Bit textures are for Madden / NCAA due to a glitch. For other games I turn that off.

I turn Ansiotropic Filtering off completely in GSdx, as it seems to give me a smoother frame rate.

As far as raising the FPS limit for PAL games, I found that using the PAL default (50.00 FPS) is a good starting point for frame rate adjusts. Some games you can tell were made for PAL or NTSC and the speed is too fast or too slow. I have taken some NTSC games (59.94) down to 50.00 (in the .ini file) or 48.00 (frame rate adjust in PCSX2) and it fixed NTSC games that were too fast.

Some games run smoother than others when you use custom frame rates. Some games I have just don't work too well when you manually adjust it. It depends on the game I think. I also think when you frame rate adjust, it is best to set your SPU to async mix.